Implantable lead affixation structure for nerve stimulation to alleviate bladder dysfunction and other indication

ABSTRACT

Anchoring devices and methods for affixing an implanted lead of a neurostimulation system at a target location in a patient are provided herein. Such anchoring devices includes a helical body having a plurality of tines extending laterally outward from the lead when deployed that engage tissue to inhibit axial movement of the implanted lead. The plurality of tines are biased towards the laterally extended deployed configuration and fold inward towards the lead to a delivery configuration to facilitate delivery of the lead through a sheath. The tines may be angled in a proximal direction or in both proximal and distal directions and may include various features to assist in visualization and delivery of the lead. The anchor may be formed according to various methods, including laser cutting of a tubular section along with heat or reflow to set the material with the anchor in the deployed configuration and injection molding.

CROSS-REFERENCES TO RELATED APPLICATIONS

The present application is a Non-Provisional of and claims the benefitof priority of U.S. Provisional Application No. 62/038,122 filed on Aug.15, 2014 and U.S. Provisional Application No. 62/110,274 filed on Jan.30, 2015; each of which is incorporated herein by reference in itsentirety.

The present application is also related to concurrently filed U.S.Non-Provisional patent application Ser. No. 14/827,081, entitled“External Pulse Generator Device and Associated Methods for Trial NerveStimulation;” U.S. Non-Provisional patent application Ser. No.14/827,108, entitled “Electromyographic Lead Positioning and StimulationTitration in a Nerve Stimulation System for Treatment of OveractiveBladder;” U.S. Non-Provisional patent application Ser. No. 14/827,095,entitled “Integrated Electromyographic Clinician Programmer For Use Withan Implantable Neurostimulator;” and U.S. Non-Provisional patentapplication Ser. No. 14/827,067, entitled “Systems and Methods forNeurostimulation Electrode Configurations Based on Neural Localization;”and U.S. Provisional Application Nos. 62/101,666, entitled “PatientRemote and Associated Methods of Use With a Nerve Stimulation System”filed on Jan. 9, 2015; 62/101,884, entitled “Attachment Devices andAssociated Methods of Use With a Nerve Stimulation Charging Device”filed on Jan. 9, 2015; 62/101,782, entitled “Improved Antenna andMethods of Use For an Implantable Nerve Stimulator” filed on Jan. 9,2015; and 62/191,134, entitled “Implantable Nerve Stimulator HavingInternal Electronics Without ASIC and Methods of Use” filed on Jul. 10,2015; each of which is assigned to the same assignee and incorporatedherein by reference in its entirety for all purposes.

FIELD OF THE INVENTION

The present invention relates to neurostimulation treatment systems andassociated devices, as well as methods of treatment, implantation andconfiguration of such treatment systems.

BACKGROUND OF THE INVENTION

Treatments with implantable neurostimulation systems have becomeincreasingly common in recent years. While such systems have shownpromise in treating a number of conditions, effectiveness of treatmentmay vary considerably between patients. A number of factors may lead tothe very different outcomes that patients experience, and viability oftreatment can be difficult to determine before implantation. Forexample, stimulation systems often make use of an array of electrodes totreat one or more target nerve structures. The electrodes are oftenmounted together on a multi-electrode lead, and the lead implanted intissue of the patient at a position that is intended to result inelectrical coupling of the electrode to the target nerve structure,typically with at least a portion of the coupling being provided viaintermediate tissues. Other approaches may also be employed, forexample, with one or more electrodes attached to the skin overlying thetarget nerve structures, implanted in cuffs around a target nerve, orthe like. Regardless, the physician will typically seek to establish anappropriate treatment protocol by varying the electrical stimulationthat is applied to the electrodes.

Current stimulation electrode placement/implantation techniques andknown treatment setting techniques suffer from significantdisadvantages. The nerve tissue structures of different patients can bequite different, with the locations and branching of nerves that performspecific functions and/or enervate specific organs being challenging toaccurately predict or identify. The electrical properties of the tissuestructures surrounding a target nerve structure may also be quitedifferent among different patients, and the neural response tostimulation may be markedly dissimilar, with an electrical stimulationpulse pattern, pulse width, frequency, and/or amplitude that iseffective to affect a body function of one patient and potentiallyimposing significant discomfort or pain, or having limited effect, onanother patient. Even in patients where implantation of aneurostimulation system provides effective treatment, frequentadjustments and changes to the stimulation protocol are often requiredbefore a suitable treatment program can be determined, often involvingrepeated office visits and significant discomfort for the patient beforeefficacy is achieved. While a number of complex and sophisticated leadstructures and stimulation setting protocols have been implemented toseek to overcome these challenges, the variability in lead placementresults, the clinician time to establish suitable stimulation signals,and the discomfort (and in cases the significant pain) that is imposedon the patient remain less than ideal. In addition, the lifetime andbattery life of such devices is relatively short, such that implantedsystems are routinely replaced every few years, which requiresadditional surgeries, patient discomfort, and significant costs tohealthcare systems.

Furthermore, since the morphology of the nerve structures varyconsiderably between patients, placement and alignment ofneurostimulation leads relative the targeted nerve structures can bedifficult to control, which can lead to inconsistent placement,unpredictable results and widely varying patient outcomes. For thesereasons, neurostimulation leads typically include multiple electrodeswith the hope that at least one electrode or a pair of electrodes willbe disposed in a location suitable for delivering neurostimulation. Onedrawback with this approach is that repeated office visits may berequired to determine the appropriate electrodes to use and/or to arriveat a neurostimulation program that delivers effective treatment. Often,the number of usable neurostimulation programs may be limited byimprecise lead placement.

The tremendous benefits of these neural stimulation therapies have notyet been fully realized. Therefore, it is desirable to provide improvedneurostimulation methods, systems and devices, as well as methods forimplanting such neurostimulation systems for a particular patient orcondition being treated. It would be particularly helpful to providesuch systems and methods so as to improve ease of use by the physicianin positioning and affixation of such leads to ensure proper leadplacement is maintained after implantation so as to provide consistentand predictable results upon delivery of neurostimulation therapy.Therefore, it is desirable to provide methods and devices for implantingneurostimulation leads that improve anchoring of the lead and allow forreduced delivery profile of the lead during implantation.

BRIEF SUMMARY OF THE INVENTION

The present invention relates to implantable neurostimulation systems,and in particular to devices and methods for anchoring implantedneurostimulation leads. In one aspect, the invention includes ananchoring body extending helically about the lead and a plurality oftines disposed along the anchoring body. The plurality of tines arebiased toward a deployed position in which the tines extend laterallyoutward from the helical body so as to engage tissue sufficiently toinhibit axial displacement of the implanted lead. The tines areconstructed so as to be resiliently deflectable toward the helical bodyduring implantation so as to fold inward toward the helical anchoringbody when constrained by a delivery sheath to facilitate delivery to thetarget location during implantation.

In one aspect, a neurostimulation system in accordance with aspect ofthe invention includes an implantable lead having one or more conductorsdisposed within a lead body, the one or more conductors extending from aproximal end of the lead to one or more neurostimulation electrodesdisposed at or near a distal end of the lead; a pulse generatorcoupleable to the proximal end of the implantable lead, the pulsegenerator being electrically coupled with the one or moreneurostimulation electrodes when coupled to the implantable lead, thepulse generator being configured to generate a plurality of electricalimpulses for delivering a neurostimulation treatment to a patientthrough the one or more neurostimulation electrodes when implanted at atarget location; and an anchor coupled with the lead body just proximalof the electrodes.

In one aspect, the anchor includes a helical body extending helically onthe outside of the lead body along a longitudinal axis thereof and aplurality of tines extending laterally away from the helical body. Eachof the plurality of tines is biased to a deployed configuration and adelivery configuration. In the deployed configuration, the plurality oftines extend laterally away from longitudinal axis when the helical bodyis disposed thereon, and in the delivery configuration, the plurality oftines are folded inward toward the longitudinal axis of the lead body tofacilitate delivery of the neurostimulation lead during implantation. Incertain embodiments, the anchor is configured such that, in the deliveryconfiguration, each of the plurality of tines is folded against the leadbody so as to further reduce the delivery profile and, in the deliveryconfiguration, the anchor has a cross-section or crossing profilecompatible with a sheath having a diameter of 5 French or higher. Incertain embodiments, the helical body and the plurality of tines areintegrally formed of the same material, while in other embodiments thetines may be separate elements attached to the helical body. The tinesare formed of a material with sufficient stiffness so that engagement oftissue with the plurality of tines inhibits axial movement of the leadwhen implanted in a tissue of the patient at the target location. Insome embodiments, the anchor may be molded from a polyurethane basedmaterial having a shore hardness within a range between 50 A and 80 D.In other embodiments, the anchor may be formed of a metal, such as ashape-memory alloy. In still other embodiments, the anchor may be formedof a combination of materials, such as a polymer based material and ametal, such as a shape-memory alloy wire.

In certain embodiments, the anchor is dimensioned so that the helicalbody extends a length between 10 mm to 30 mm along the lead body whencoupled thereon, preferably about 20 mm. Each of the plurality of tinesmay extend laterally outward from the longitudinal axis a distancebetween 1 mm to 4 mm. Each of the plurality of tines may be between 1.5mm to 3 mm in length and between 0.5 mm to 2.0 mm in width. In someembodiments, the plurality of tines include tines of varying length,width and angle in the proximal direction, while in other embodiments,the plurality of tines may be of differing lengths or may angle in bothproximal and distal directions. The plurality of tines may have agenerally rectangular tab shape and may include rounded or chamferedcorners and/or edges so as to inhibit tissue damage at the cornersand/or edges. In some embodiments, the tines are biased toward an anglebetween 30 to 80 degrees from the longitudinal axis in the deployedconfiguration.

In one aspect, the helical body attaches to the lead body in ananchoring portion having a recessed portion with a reduced profile so asto further reduce the cross section, such as to 2 mm or less so as toaccommodate a 5 French sheath for use in implanting the lead. In someembodiments, the anchor includes multiple anchor sections that may beattached to one another and deployed adjacent one another. This featuremay allow the user to customize the anchoring portion as to both lengthand tine direction of the anchor, by reverse the anchors or combiningdiffering types of anchors within the anchoring portion. The anchor mayfurther include one or more additional features, including any of: aradiopaque element extending a substantial length of the helical body soas to facilitate positioning using visualization techniques; an embeddedshield material suitable for shielding magnetic resonance inducedheating; and biodegradable or drug eluting tines.

In certain embodiments, the helical body is a continuous helical flapand the plurality of tines comprise a plurality of sections of thecontinuous helical flap, the plurality of section defined by a pluralityof cuts along a length of the continuous helical flap so as to allow theplurality of sections to fold inward without overlapping one another.

In other embodiments, the anchor is formed by laser cutting a tubularportion of a material (e.g. polymer or metal, such as Nitinol) andsetting the material while the anchor is in the deployed configurationby heat setting or reflow. In still other embodiments, the anchor may beformed by injection molding a polymer material in a multi-piece moldassembly, which allows for further variability in the anchor structure,such as varying thicknesses in different portions of the anchor.

Further areas of applicability of the present disclosure will becomeapparent from the detailed description provided hereinafter. It shouldbe understood that the detailed description and specific examples, whileindicating various embodiments, are intended for purposes ofillustration only and are not intended to necessarily limit the scope ofthe disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically illustrates a nerve stimulation system, whichincludes a clinician programmer and a patient remote used in positioningand/or programming of both a trial neurostimulation system and apermanently implanted neurostimulation system, in accordance withaspects of the invention.

FIGS. 2A-2C show diagrams of the nerve structures along the spine, thelower back and sacrum region, which may be stimulated in accordance withaspects of the invention.

FIG. 3A shows an example of a fully implanted neurostimulation system inaccordance with aspects of the invention.

FIG. 3B shows an example of a neurostimulation system having a partlyimplanted stimulation lead and an external pulse generator adhered tothe skin of the patient for use in a trial stimulation, in accordancewith aspects of the invention.

FIG. 4 shows an example of a neurostimulation system having animplantable stimulation lead, an implantable pulse generator, and anexternal charging device, in accordance with aspects of the invention.

FIG. 5A-5C show detail views of an implantable pulse generator andassociated components for use in a neurostimulation system, inaccordance with aspects of the invention.

FIGS. 6A-6C show a strain relief structure for use with aneurostimulation lead and implantable pulse generator, in accordancewith aspects of the invention.

FIG. 7 illustrates a neurostimulation lead with an anchor structurethereon, in accordance with aspects of the invention.

FIG. 8 illustrates an example anchor structure, in accordance withaspects of the invention.

FIGS. 9A-9B illustrate a neurostimulation lead with an anchor structurethereon before and after deployment, in accordance with aspects of theinvention.

FIGS. 10A-10B illustrate an example anchor structure, in accordance withaspects of the invention.

FIGS. 11A-11B illustrate an example anchor structure, in accordance withaspects of the invention.

FIGS. 12A-12B illustrate an example anchor structure, in accordance withaspects of the invention.

FIGS. 13A-13B illustrate an example anchor structure, in accordance withaspects of the invention.

FIGS. 14A-14B illustrate an example anchor structure, in accordance withaspects of the invention.

FIGS. 15A-15C illustrate an example anchor structure before and afterdeployment and FIG. 15C illustrates an end view of the deployed anchorstructure, in accordance with aspects of the invention.

FIGS. 16A-16B illustrate an example anchor structure formed by lasercutting, the structure shown before and after deployment, in accordancewith aspects of the invention.

FIGS. 17A-17B illustrate an alternative illustrate an example anchorstructure formed by an injection molding process, in accordance withaspects of the invention.

FIGS. 18-20 illustrate methods of forming an anchor and methods ofanchoring a neurostimulation lead in accordance with aspects of theinvention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to neurostimulation treatment systems andassociated devices, as well as methods of treatment,implantation/placement and configuration of such treatment systems. Inparticular embodiments, the invention relates to sacral nervestimulation treatment systems configured to treat bladder dysfunctions,including overactive bladder (“OAB”), as well as fecal dysfunctions andrelieve symptoms associated therewith. It will be appreciated howeverthat the present invention may also be utilized for the treatment ofpain or other indications, such as movement or affective disorders, aswill be appreciated by one of skill in the art.

I. Neurostimulation Indications

Neurostimulation treatment systems, such as any of those describedherein, can be used to treat a variety of ailments and associatedsymptoms, such as acute pain disorders, movement disorders, affectivedisorders, as well as bladder related dysfunction and bowel and fecaldysfunction. Examples of pain disorders that may be treated byneurostimulation include failed back surgery syndrome, reflexsympathetic dystrophy or complex regional pain syndrome, causalgia,arachnoiditis, and peripheral neuropathy. Movement orders include muscleparalysis, tremor, dystonia and Parkinson's disease. Affective disordersinclude depressions, obsessive-compulsive disorder, cluster headache,Tourette syndrome and certain types of chronic pain. Bladder relateddysfunctions include but are not limited to OAB, urge incontinence,urgency-frequency, and urinary retention. OAB can include urgeincontinence and urgency-frequency alone or in combination. Urgeincontinence is the involuntary loss or urine associated with a sudden,strong desire to void (urgency). Urgency-frequency is the frequent,often uncontrollable urges to urinate (urgency) that often result invoiding in very small amounts (frequency). Urinary retention is theinability to empty the bladder. Neurostimulation treatments can beconfigured to address a particular condition by effectingneurostimulation of targeted nerve tissues relating to the sensoryand/or motor control associated with that condition or associatedsymptom.

In one aspect, the methods and systems described herein are particularlysuited for treatment of urinary and fecal dysfunctions. These conditionshave been historically under-recognized and significantly underserved bythe medical community. OAB is one of the most common urinarydysfunctions. It is a complex condition characterized by the presence ofbothersome urinary symptoms, including urgency, frequency, nocturia andurge incontinence. It is estimated that about 40 million Americanssuffer from OAB. Of the adult population, about 16% of all men and womenlive with OAB symptoms.

OAB symptoms can have a significant negative impact on the psychosocialfunctioning and the quality of life of patients. People with OAB oftenrestrict activities and/or develop coping strategies. Furthermore, OABimposes a significant financial burden on individuals, their families,and healthcare organizations. The prevalence of co-morbid conditions isalso significantly higher for patients with OAB than in the generalpopulation. Co-morbidities may include falls and fractures, urinarytract infections, skin infections, vulvovaginitis, cardiovascular, andcentral nervous system pathologies. Chronic constipation, fecalincontinence, and overlapping chronic constipation occur more frequentlyin patients with OAB.

Conventional treatments of OAB generally include lifestyle modificationsas a first course of action. Lifestyle modifications include eliminatingbladder irritants (such as caffeine) from the diet, managing fluidintake, reducing weight, stopping smoking, and managing bowelregularity. Behavioral modifications include changing voiding habits(such as bladder training and delayed voiding), training pelvic floormuscles to improve strength and control of urethral sphincter,biofeedback and techniques for urge suppression. Medications areconsidered a second-line treatment for OAB. These includeanti-cholinergic medications (oral, transdermal patch, and gel) and oralbeta-3 adrenergic agonists. However, anti-cholinergics are frequentlyassociated with bothersome, systemic side effects including dry mouth,constipation, urinary retention, blurred vision, somnolence, andconfusion. Studies have found that more than 50% of patients stop usinganti-cholinergic medications within 90 days due to a lack of benefit,adverse events, or cost.

When these approaches are unsuccessful, third-line treatment optionssuggested by the American Urological Association include intradetrusor(bladder smooth muscle) injections of botulinum toxin (BTX),Percutaneous Tibial Nerve Stimulation (PTNS) and Sacral NerveStimulation (SNM). BTX is administered via a series of intradetrusorinjections under cystoscopic guidance, but repeat injections of BTX aregenerally required every 4 to 12 months to maintain effect and BTX mayundesirably result in urinary retention. A number or randomizedcontrolled studies have shown some efficacy of BTX injections in OABpatients, but long-term safety and effectiveness of BTX for OAB islargely unknown.

PTNS therapy consists of weekly, 30-minute sessions over a period of 12weeks, each session using electrical stimulation that is delivered froma hand-held stimulator to the sacral plexus via the tibial nerve. Forpatients who respond well and continue treatment, ongoing sessions,typically every 3-4 weeks, are needed to maintain symptom reduction.There is potential for declining efficacy if patients fail to adhere tothe treatment schedule. Efficacy of PTNS has been demonstrated in a fewrandomized-controlled studies, however, there is limited data on PTNSeffectiveness beyond 3-years and PTNS is not recommended for patientsseeking a cure for urge urinary incontinence (UUI) (e.g., 100% reductionin incontinence episodes) (EAU Guidelines).

II. Sacral Neuromodulation

SNM is an established therapy that provides a safe, effective,reversible, and long-lasting treatment option for the management of urgeincontinence, urgency-frequency, and non-obstructive urinary retention.SNM therapy involves the use of mild electrical pulses to stimulate thesacral nerves located in the lower back. Electrodes are placed next to asacral nerve, usually at the S3 level, by inserting the electrode leadsinto the corresponding foramen of the sacrum. The electrodes areinserted subcutaneously and are subsequently attached to an implantablepulse generator (IPG). The safety and effectiveness of SNM for thetreatment of OAB, including durability at five years for both urgeincontinence and urgency-frequency patients, is supported by multiplestudies and is well-documented. SNM has also been approved to treatchronic fecal incontinence in patients who have failed or are notcandidates for more conservative treatments.

A. Implantation of Sacral Neuromodulation System

Currently, SNM qualification has a trial phase, and is followed ifsuccessful by a permanent implant. The trial phase is a test stimulationperiod where the patient is allowed to evaluate whether the therapy iseffective. Typically, there are two techniques that are utilized toperform the test stimulation. The first is an office-based proceduretermed the Percutaneous Nerve Evaluation (PNE) and the other is a stagedtrial.

In the PNE, a foramen needle is typically used first to identify theoptimal stimulation location, usually at the S3 level, and to evaluatethe integrity of the sacral nerves. Motor and sensory responses are usedto verify correct needle placement, as described in Table 1 below. Atemporary stimulation lead (a unipolar electrode) is then placed nearthe sacral nerve under local anesthesia. This procedure can be performedin an office setting without fluoroscopy. The temporary lead is thenconnected to an external pulse generator (EPG) taped onto the skin ofthe patient during the trial phase. The stimulation level can beadjusted to provide an optimal comfort level for the particular patient.The patient will monitor his or her voiding for 3 to 7 days to see ifthere is any symptom improvement. The advantage of the PNE is that it isan incision free procedure that can be performed in the physician'soffice using local anesthesia. The disadvantage is that the temporarylead is not securely anchored in place and has the propensity to migrateaway from the nerve with physical activity and thereby cause failure ofthe therapy. If a patient fails this trial test, the physician may stillrecommend the staged trial as described below. If the PNE trial ispositive, the temporary trial lead is removed and a permanentquadri-polar tined lead is implanted along with an IPG under generalanesthesia.

A staged trial involves the implantation of the permanent quadri-polartined stimulation lead into the patient from the start. It also requiresthe use of a foramen needle to identify the nerve and optimalstimulation location. The lead is implanted near the S3 sacral nerve andis connected to an EPG via a lead extension. This procedure is performedunder fluoroscopic guidance in an operating room and under local orgeneral anesthesia. The EPG is adjusted to provide an optimal comfortlevel for the patient and the patient monitors his or her voiding for upto two weeks. If the patient obtains meaningful symptom improvement, heor she is considered a suitable candidate for permanent implantation ofthe IPG under general anesthesia, typically in the upper buttock area,as shown in FIGS. 1 and 3A.

TABLE 1 Motor and Sensory Responses of SNM at Different Sacral NerveRoots Response Nerve Innervation Pelvic Floor Foot/calf/leg Sensation S2-Primary somatic “Clamp” * of anal Leg/hip rotation, Contraction of basecontributor of pudendal sphincter plantar flexion of entire of penis,vagina nerve for external foot, contraction of calf sphincter, leg, footS3 - Virtually all pelvic “bellows” ** of Plantar flexion of greatPulling in rectum, autonomic functions and perineum toe, occasionallyother extending forward striated mucle (levetor toes to scrotum or labiaani) S4 - Pelvic autonomic “bellows” ** No lower extremity Pulling inrectum and somatic; No leg pr motor stimulation only foot * Clamp:contraction of anal sphincter and, in males, retraction of base ofpenis. Move buttocks aside and look for anterior/posterior shortening ofthe perineal structures. ** Bellows: lifting and dropping of pelvicfloor. Look for deepening and flattening of buttock groove

In regard to measuring outcomes for SNM treatment of voidingdysfunction, the voiding dysfunction indications (e.g., urgeincontinence, urgency-frequency, and non-obstructive urinary retention)are evaluated by unique primary voiding diary variables. The therapyoutcomes are measured using these same variables. SNM therapy isconsidered successful if a minimum of 50% improvement occurs in any ofprimary voiding diary variables compared with the baseline. For urgeincontinence patients, these voiding diary variables may include: numberof leaking episodes per day, number of heavy leaking episodes per day,and number of pads used per day. For patients with urgency-frequency,primary voiding diary variables may include: number of voids per day,volume voided per void and degree of urgency experienced before eachvoid. For patients with retention, primary voiding diary variables mayinclude: catheterized volume per catheterization and number ofcatheterizations per day. For fecal incontinence patients, the outcomemeasures captured by the voiding diary include: number of leakingepisodes per week, number of leaking days per week, and degree ofurgency experienced before each leak.

The mechanism of action of SNM is multifactorial and impacts theneuro-axis at several different levels. In patients with OAB, it isbelieved that pudendal afferents can activate the inhibitory reflexesthat promote bladder storage by inhibiting the afferent limb of anabnormal voiding reflex. This blocks input to the pontine micturitioncenter, thereby restricting involuntary detrusor contractions withoutinterfering with normal voiding patterns. For patients with urinaryretention, SNM is believed to activate the pudendal nerve afferentsoriginating from the pelvic organs into the spinal cord. At the level ofthe spinal cord, pudendal afferents may turn on voiding reflexes bysuppressing exaggerated guarding reflexes, thus relieving symptoms ofpatients with urinary retention so normal voiding can be facilitated. Inpatients with fecal incontinence, it is hypothesized that SNM stimulatespudendal afferent somatic fibers that inhibit colonic propulsiveactivity and activates the internal anal sphincter, which in turnimproves the symptoms of fecal incontinence patients.

The present invention relates to a system adapted to deliverneurostimulation to targeted nerve tissues in a manner that results inpartial or complete activation of the target nerve fibers, causes theaugmentation or inhibition of neural activity in nerves, potentially thesame or different than the stimulation target, that control the organsand structures associated with bladder and bowel function.

B. EMG Assisted Neurostimulation Lead Placement and Programming

While conventional sacral nerve stimulation approaches have shownefficacy in treatment of bladder and bowel related dysfunctions, thereexists a need to improve positioning of the neurostimulation leads andconsistency between the trial and permanent implantation positions ofthe lead as well as to improve methods of programming. Neurostimulationrelies on consistently delivering therapeutic stimulation from a pulsegenerator, via one or more neurostimulation electrodes, to particularnerves or targeted regions. The neurostimulation electrodes are providedon a distal end of an implantable lead that can be advanced through atunnel formed in patient tissue. Implantable neurostimulation systemsprovide patients with great freedom and mobility, but it may be easierto adjust the neurostimulation electrodes of such systems before theyare surgically implanted. It is desirable for the physician to confirmthat the patient has desired motor and/or sensory responses beforeimplanting an IPG. For at least some treatments (including treatments ofat least some forms of urinary and/or fecal dysfunction), demonstratingappropriate motor responses may be highly beneficial for accurate andobjective lead placement while the sensory response may not be requiredor not available (e.g., patient is under general anesthesia).

Placement and calibration of the neurostimulation electrodes andimplantable leads sufficiently close to specific nerves can bebeneficial for the efficacy of treatment. Accordingly, aspects andembodiments of the present disclosure are directed to aiding andrefining the accuracy and precision of neurostimulation electrodeplacement. Further, aspects and embodiments of the present disclosureare directed to aiding and refining protocols for setting therapeutictreatment signal parameters for a stimulation program implementedthrough implanted neurostimulation electrodes.

Prior to implantation of the permanent device, patients may undergo aninitial testing phase to estimate potential response to treatment. Asdiscussed above, PNE may be done under local anesthesia, using a testneedle to identify the appropriate sacral nerve(s) according to asubjective sensory response by the patient. Other testing procedures caninvolve a two-stage surgical procedure, where a quadri-polar tined leadis implanted for a testing phase (Stage 1) to determine if patients showa sufficient reduction in symptom frequency, and if appropriate,proceeding to the permanent surgical implantation of a neuromodulationdevice. For testing phases and permanent implantation, determining thelocation of lead placement can be dependent on subjective qualitativeanalysis by either or both of a patient or a physician.

In exemplary embodiments, determination of whether or not an implantablelead and neurostimulation electrode is located in a desired or correctlocation can be accomplished through use of electromyography (“EMG”),also known as surface electromyography. EMG, is a technique that uses anEMG system or module to evaluate and record electrical activity producedby muscles, producing a record called an electromyogram. EMG detects theelectrical potential generated by muscle cells when those cells areelectrically or neurologically activated. The signals can be analyzed todetect activation level or recruitment order. EMG can be performedthrough the skin surface of a patient, intramuscularly or throughelectrodes disposed within a patient near target muscles, or using acombination of external and internal structures. When a muscle or nerveis stimulated by an electrode, EMG can be used to determine if therelated muscle is activated, (i.e. whether the muscle fully contracts,partially contracts, or does not contract) in response to the stimulus.Accordingly, the degree of activation of a muscle can indicate whetheran implantable lead or neurostimulation electrode is located in thedesired or correct location on a patient. Further, the degree ofactivation of a muscle can indicate whether a neurostimulation electrodeis providing a stimulus of sufficient strength, amplitude, frequency, orduration to affect a treatment regimen on a patient. Thus, use of EMGprovides an objective and quantitative means by which to standardizeplacement of implantable leads and neurostimulation electrodes, reducingthe subjective assessment of patient sensory responses.

In some approaches, positional titration procedures may optionally bebased in part on a paresthesia or pain-based subjective response from apatient. In contrast, EMG triggers a measureable and discrete muscularreaction. As the efficacy of treatment often relies on precise placementof the neurostimulation electrodes at target tissue locations and theconsistent, repeatable delivery of neurostimulation therapy, using anobjective EMG measurement can substantially improve the utility andsuccess of SNM treatment. The measureable muscular reaction can be apartial or a complete muscular contraction, including a response belowthe triggering of an observable motor response, such as those shown inTable 1, depending on the stimulation of the target muscle. In addition,by utilizing a trial system that allows the neurostimulation lead toremain implanted for use in the permanently implanted system, theefficacy and outcome of the permanently implanted system is moreconsistent with the results of the trial period, which moreover leads toimproved patient outcomes.

C. Example System Embodiments

FIG. 1 schematically illustrates example nerve stimulation systemsetups, which includes a setup for use in a trial neurostimulationsystem 200 and a setup for use in a permanently implantedneurostimulation system 100, in accordance with aspects of theinvention. The EPG 80 and IPG 50 are each compatible with and wirelesslycommunicate with a clinician programmer (CP) 60 and a patient remote 70,which are used in positioning and/or programming the trialneurostimulation system 200 and/or permanently implanted system 100after a successful trial. As discussed above, the system utilizes acable set and EMG sensor patches in the trial system setup 100 tofacilitate lead placement and neurostimulation programming. CP caninclude specialized software, specialized hardware, and/or both, to aidin lead placement, programming, re-programming, stimulation control,and/or parameter setting. In addition, each of the IPG and the EPGallows the patient at least some control over stimulation (e.g.,initiating a pre-set program, increasing or decreasing stimulation),and/or to monitor battery status with the patient remote. This approachalso allows for an almost seamless transition between the trial systemand the permanent system.

In one aspect, the CP 60 is used by a physician to adjust the settingsof the EPG and/or IPG while the lead is implanted within the patient.The CP can be a tablet computer used by the clinician to program theIPG, or to control the EPG during the trial period. The CP can alsoinclude capability to record stimulation-induced electromyograms tofacilitate lead placement and programming. The patient remote 70 canallow the patient to turn the stimulation on or off, or to varystimulation from the IPG while implanted, or from the EPG during thetrial phase.

In another aspect, the CP 60 has a control unit which can include amicroprocessor and specialized computer-code instructions forimplementing methods and systems for use by a physician in deploying thetreatment system and setting up treatment parameters. The CP generallyincludes a graphical user interface, an EMG module, an EMG input thatcan couple to an EMG output stimulation cable, an EMG stimulation signalgenerator, and a stimulation power source. The stimulation cable canfurther be configured to couple to any or all of an access device (e.g.,a foramen needle), a treatment lead of the system, or the like. The EMGinput may be configured to be coupled with one or more sensory patchelectrode(s) for attachment to the skin of the patient adjacent a muscle(e.g., a muscle enervated by a target nerve). Other connectors of the CPmay be configured for coupling with an electrical ground or groundpatch, an electrical pulse generator (e.g., an EPG or an IPG), or thelike. As noted above, the CP can include a module with hardware andcomputer-code to execute EMG analysis, where the module can be acomponent of the control unit microprocessor, a pre-processing unitcoupled to or in-line with the stimulation and/or sensory cables, or thelike.

In other aspects, the CP 60 allows the clinician to read the impedanceof each electrode contact whenever the lead is connected to an EPG, anIPG or a CP to ensure reliable connection is made and the lead isintact. This may be used as an initial step in both positioning the leadand in programming the leads to ensure the electrodes are properlyfunctioning. The CP 60 is also able to save and display previous (e.g.,up to the last four) programs that were used by a patient to helpfacilitate re-programming. In some embodiments, the CP 60 furtherincludes a USB port for saving reports to a USB drive and a chargingport. The CP is configured to operate in combination with an EPG whenplacing leads in a patient body as well with the IPG during programming.The CP can be electronically coupled to the EPG during test simulationthrough a specialized cable set or through wireless communication,thereby allowing the CP to configure, modify, or otherwise program theelectrodes on the leads connected to the EPG. The CP may also includephysical on/off buttons to turn the CP on and off and/or to turnstimulation on and off.

The electrical pulses generated by the EPG and IPG are delivered to oneor more targeted nerves via one or more neurostimulation electrodes ator near a distal end of each of one or more leads. The leads can have avariety of shapes, can be a variety of sizes, and can be made from avariety of materials, which size, shape, and materials can be tailoredto the specific treatment application. While in this embodiment, thelead is of a suitable size and length to extend from the IPG and throughone of the foramen of the sacrum to a targeted sacral nerve, in variousother applications, the leads may be, for example, implanted in aperipheral portion of the patient's body, such as in the arms or legs,and can be configured to deliver electrical pulses to the peripheralnerve such as may be used to relieve chronic pain. It is appreciatedthat the leads and/or the stimulation programs may vary according to thenerves being targeted.

FIGS. 2A-2C show diagrams of various nerve structures of a patient,which may be used in neurostimulation treatments, in accordance withaspects of the invention. FIG. 2A shows the different sections of thespinal cord and the corresponding nerves within each section. The spinalcord is a long, thin bundle of nerves and support cells that extend fromthe brainstem along the cervical cord, through the thoracic cord and tothe space between the first and second lumbar vertebra in the lumbarcord. Upon exiting the spinal cord, the nerve fibers split into multiplebranches that innervate various muscles and organs transmitting impulsesof sensation and control between the brain and the organs and muscles.Since certain nerves may include branches that innervate certain organs,such as the bladder, and branches that innervate certain muscles of theleg and foot, stimulation of the nerve at or near the nerve root nearthe spinal cord can stimulate the nerve branch that innervate thetargeted organ, which may also result in muscle responses associatedwith the stimulation of the other nerve branch. Thus, by monitoring forcertain muscle responses, such as those in Table 1, either visually,through the use of EMG as described herein or both, the physician candetermine whether the targeted nerve is being stimulated. Whilestimulation at a certain level may evoke robust muscle responses visibleto the naked eye, stimulation at a lower level (e.g. sub-threshold) maystill provide activation of the nerve associated with the targeted organwhile evoking no corresponding muscle response or a response onlyvisible with EMG. In some embodiments, this low level stimulation alsodoes not cause any paresthesia. This is advantageous as it allows fortreatment of the condition by neurostimulation without otherwise causingpatient discomfort, pain or undesired muscle responses.

FIG. 2B shows the nerves associated with the lower back section, in thelower lumbar cord region where the nerve bundles exit the spinal cordand travel through the sacral foramens of the sacrum. In someembodiments, the neurostimulation lead is advanced through the foramenuntil the neurostimulation electrodes are positioned at the anteriorsacral nerve root, while the anchoring portion of the lead proximal ofthe stimulation electrodes are generally disposed dorsal of the sacralforamen through which the lead passes, so as to anchor the lead inposition. FIG. 2C shows detail views of the nerves of the lumbosacraltrunk and the sacral plexus, in particular, the S1-S5 nerves of thelower sacrum. The S3 sacral nerve is of particular interest fortreatment of bladder related dysfunction, and in particular OAB.

FIG. 3A schematically illustrates an example of a fully implantedneurostimulation system 100 adapted for sacral nerve stimulation.Neurostimulation system 100 includes an IPG implanted in a lower backregion and connected to a neurostimulation lead extending through the S3foramen for stimulation of the S3 sacral nerve. The lead is anchored bya tined anchor portion 10 that maintains a position of a set ofneurostimulation electrodes 30 along the targeted nerve, which in thisexample, is the anterior sacral nerve root S3 which enervates thebladder so as to provide therapy for various bladder relateddysfunctions. While this embodiment is adapted for sacral nervestimulation, it is appreciated that similar systems can be used intreating patients with, for example, chronic, severe, refractoryneuropathic pain originating from peripheral nerves or various urinarydysfunctions or still further other indications. Implantableneurostimulation systems can be used to either stimulate a targetperipheral nerve or the posterior epidural space of the spine.

Properties of the electrical pulses can be controlled via a controllerof the implanted pulse generator. In some embodiments, these propertiescan include, for example, the frequency, amplitude, pattern, duration,or other aspects of the electrical pulses. These properties can include,for example, a voltage, a current, or the like. This control of theelectrical pulses can include the creation of one or more electricalpulse programs, plans, or patterns, and in some embodiments, this caninclude the selection of one or more pre-existing electrical pulseprograms, plans, or patterns. In the embodiment depicted in FIG. 3A, theimplantable neurostimulation system 100 includes a controller in the IPGhaving one or more pulse programs, plans, or patterns that may bepre-programmed or created as discussed above. In some embodiments, thesesame properties associated with the IPG may be used in an EPG of apartly implanted trial system used before implantation of the permanentneurostimulation system 100.

FIG. 3B shows a schematic illustration of a trial neurostimulationsystem 200 utilizing an EPG patch 81 adhered to the skin of a patient,particularly to the abdomen of a patient, the EPG 80 being encasedwithin the patch. In one aspect, the lead is hardwired to the EPG, whilein another the lead is removably coupled to the EPG through a port oraperture in the top surface of the flexible patch 81. Excess lead can besecured by an additional adherent patch. In one aspect, the EPG patch isdisposable such that the lead can be disconnected and used in apermanently implanted system without removing the distal end of the leadfrom the target location. Alternatively, the entire system can bedisposable and replaced with a permanent lead and IPG. When the lead ofthe trial system is implanted, an EMG obtained via the CP using one ormore sensor patches can be used to ensure that the leads are placed at alocation proximate to the target nerve or muscle, as discussedpreviously.

In some embodiments, the trial neurostimulation system utilizes an EPG80 within an EPG patch 81 that is adhered to the skin of a patient andis coupled to the implanted neurostimulation lead 20 through a leadextension 22, which is coupled with the lead 20 through a connector 21.This extension and connector structure allows the lead to be extended sothat the EPG patch can be placed on the abdomen and allows use of a leadhaving a length suitable for permanent implantation should the trialprove successful. This approach may utilize two percutaneous incisions,the connector provided in the first incision and the lead extensionsextending through the second percutaneous incision, there being a shorttunneling distance (e.g., about 10 cm) there between. This technique mayalso minimize movement of an implanted lead during conversion of thetrial system to a permanently implanted system.

In one aspect, the EPG unit is wirelessly controlled by a patient remoteand/or the CP in a similar or identical manner as the IPG of apermanently implanted system. The physician or patient may altertreatment provided by the EPG through use of such portable remotes orprogrammers and the treatments delivered are recorded on a memory of theprogrammer for use in determining a treatment suitable for use in apermanently implanted system. The CP can be used in lead placement,programming and/or stimulation control in each of the trial andpermanent nerve stimulation systems. In addition, each nerve stimulationsystem allows the patient to control stimulation or monitor batterystatus with the patient remote. This configuration is advantageous as itallows for an almost seamless transition between the trial system andthe permanent system. From the patient's viewpoint, the systems willoperate in the same manner and be controlled in the same manner, suchthat the patient's subjective experience in using the trial system moreclosely matches what would be experienced in using the permanentlyimplanted system. Thus, this configuration reduces any uncertainties thepatient may have as to how the system will operate and be controlledsuch that the patient will be more likely to receive a trial system or apermanent system.

As shown in the detailed view of FIG. 3B, the EPG 80 is encased within aflexible laminated patch 81, which include an aperture or port throughwhich the EPG 80 is connected to the lead extension 22. The patch mayfurther an “on/off” button 83 with a molded tactile detail to allow thepatient to turn the EPG on and/or off through the outside surface of theadherent patch 81. The underside of the patch 81 is covered with askin-compatible adhesive 82 for continuous adhesion to a patient for theduration of the trial period. For example, a breathable strip havingskin-compatible adhesive 82 would allow the EPG 80 to remain attached tothe patient continuously during the trial, which may last over a week,typically two weeks to four weeks, or even longer.

While the above described systems provide considerable improvements inlocating an optimal position of the lead and fine tuning lead placementand an optimal neurostimulation program is determined, it is imperativeafter the lead is successfully placed to ensure that the lead positionis maintained over the course of therapy. Should the neurostimulationlead migrate, even a small axial distance, the electrodes may shift fromthe targeted nerve tissue such that the neurostimulation treatment maynot delivery consistent results or no longer provide therapeutic effectwithout reprogramming or repositioning the lead.

In a fully implantable system, the pulse generator is implanted in thepatient in an area having adequate size to comfortably contain the pulsegenerator, typically in a lower back region or lower abdominal region.Since the electrodes may need to be located a considerable distance fromthe implantable pulse generator, depending on the treatment or therapybeing delivered, a neurostimulation lead is used to deliver theelectrical pulses from the implanted pulse generator to the electrodes.While many such systems have proven effective, studies have shown thatover time the neurostimulation lead may move, particularly when the leadextends through areas subject to movement. Such movement can dislocatethe electrodes from the targeted location, such that theneurostimulation treatment becomes ineffective, requiring adjustment orreplacement of the lead. Therefore, it is desirable to provide ananchoring device on the stimulation lead in such systems to inhibitmovement of the lead and dislocation of the electrodes. Whileconventional neurostimulation has developed various anchoringmechanisms, such mechanisms often complicate the implantation procedure,undesirably increase the delivery profile of the lead, are difficult toreplace or remove, or have proven ineffective.

FIG. 4 illustrates an example neurostimulation system 100 that is fullyimplantable and adapted for sacral nerve stimulation treatment. Theimplantable system 100 includes an IPG 90 that is coupled to aneurostimulation lead 20 that includes a group of neurostimulationelectrodes 30 at a distal end of the lead. The lead includes a leadanchor portion 10 with a series of tines extending radially outward soas to anchor the lead and maintain a position of the neurostimulationlead 20 after implantation. The lead 20 may further include one or moreradiopaque markers (e.g., silicon markers) 25 to assist in locating andpositioning the lead using visualization techniques such as fluoroscopy.In some embodiments, the IPG provides monopolar or bipolar electricalpulses that are delivered to the targeted nerves through one or moreneurostimulation electrodes. In sacral nerve stimulation, the lead istypically implanted through the S3 foramen as described herein.

As can be seen in FIG. 4, the neurostimulation lead 20 includes aplurality of neurostimulation electrodes 30 at a distal end of the leadand the anchor 10 is disposed just proximal of the electrodes 30.Typically, the anchor is disposed near and proximal of the plurality ofelectrodes so as to provide anchoring of the lead relatively close tothe electrodes. This configuration is also advantageous as it allows fortesting of the neurostimulation electrodes during implantation beforedeploying of the anchor (as described below), which allows the optimallocation of the neurostimulation electrodes to be determined before thelead is anchored in place. As shown, the anchor 10 includes an anchorbody 12 helically swept about the lead body and a plurality of tines 14extending laterally outward from the helical body 12. This configurationis advantageous over conventional anchor devices as it provides aplurality of tines distributed both circumferentially and axially aboutthe lead while extending from a common anchor body, thereby simplifyingattachment and replacement of the anchoring tines. In addition, sincethe anchor body extends helically about the lead boy, this allows theflexibility of the lead body to be retained in the tined area. In oneaspect, the anchor is constructed of a suitable material that isbiocompatible as well as compatible with the material of which the leadbody is formed and that is sufficiently flexible to provide anchoringforce against the tissue without damaging the tissue.

In one aspect, the IPG is rechargeable wirelessly through conductivecoupling by use of a charging device 50 (CD), which is a portable devicepowered by a rechargeable battery to allow patient mobility whilecharging. The CD is used for transcutaneous charging of the IPG throughRF induction. The CD can either be patched to the patient's skin usingan adhesive or can be held in place using a belt 53 or by an adhesivepatch 52, such as shown in the schematic of FIG. 1. The CD may becharged by plugging the CD directly into an outlet or by placing the CDin a charging dock or station 51 that connects to an AC wall outlet orother power source

FIG. 5A-5C show detail views of the IPG and its internal components. Insome embodiments, the pulse generator can generate one or morenon-ablative electrical pulses that are delivered to a nerve to controlpain or cause some other desired effect, for example to inhibit,prevent, or disrupt neural activity for the treatment of OAB or bladderrelated dysfunction. In some applications, the pulses having a pulseamplitude in a range between 0 mA to 1,000 mA, 0 mA to 100 mA, 0 mA to50 mA, 0 mA to 25 mA, and/or any other or intermediate range ofamplitudes may be used. One or more of the pulse generators can includea processor and/or memory adapted to provide instructions to and receiveinformation from the other components of the implantableneurostimulation system. The processor can include a microprocessor,such as a commercially available microprocessor from Intel® or AdvancedMicro Devices, Inc.®, or the like. An IPG may include an energy storagefeature, such as one or more capacitors or a battery, one or morebatteries, and typically includes a wireless charging unit.

One or more properties of the electrical pulses can be controlled via acontroller of the IPG or EPG. In some embodiments, these properties caninclude, for example, the frequency, amplitude, pattern, duration, orother aspects of the timing and magnitude of the electrical pulses.These properties can further include, for example, a voltage, a current,or the like. This control of the electrical pulses can include thecreation of one or more electrical pulse programs, plans, or patterns,and in some embodiments, this can include the selection of one or morepre-existing electrical pulse programs, plans, or patterns. In oneaspect, the IPG 90 includes a controller having one or more pulseprograms, plans, or patterns that may be created and/or pre-programmed.In some embodiments, the IPG can be programmed to vary stimulationparameters including pulse amplitude in a range from 0 mA to 10 mA,pulse width in a range from 50 μs to 500 μs, pulse frequency in a rangefrom 5 Hz to 250 Hz, stimulation modes (e.g., continuous or cycling),and electrode configuration (e.g., anode, cathode, or off), to achievethe optimal therapeutic outcome specific to the patient. In particular,this allows for an optimal setting to be determined for each patienteven though each parameter may vary from person to person.

As shown in FIGS. 5A-5B, the IPG 90 may include a header portion 91 atone end and a ceramic portion 94 at the opposite end. The header portion91 houses a feed through assembly 92 and connector stack 93, while theceramic case portion 94 houses an antennae assembly 96 to facilitatewireless communication with the clinician program, the patient remote,and/or a charging coil to facilitate wireless charging with the CD. Theremainder of the IPG is covered with a titanium case portion 97, whichencases the printed circuit board, memory and controller components thatfacilitate the electrical pulse programs described above. In the exampleshown in FIG. 5C, the header portion of the IPG includes a four-pinfeed-through assembly 92 that couples with the connector stack 93 inwhich the proximal end of the lead is coupled. The four pins correspondto the four electrodes of the neurostimulation lead. In someembodiments, a Balseal® connector block is electrically connected tofour platinum/iridium alloy feed-through pins which are brazed to analumina ceramic insulator plate along with a titanium alloy flange. Thisfeed-through assembly is laser seam welded to a titanium-ceramic brazedcase to form a complete hermetic housing for the electronics.

In the IPG shown in FIG. 5A, the ceramic and titanium brazed case isutilized on one end of the IPG where the ferrite coil and PCB antennaassemblies are positioned. A reliable hermetic seal is provided via aceramic-to-metal brazing technique. The zirconia ceramic may comprise a3Y-TZP (3 mol percent Yttria-stabilized tetragonal ZirconiaPolycrystals) ceramic, which has a high flexural strength and impactresistance and has been commercially utilized in a number of implantablemedical technologies. It will be appreciated, however, that otherceramics or other suitable materials may be used for construction of theIPG.

Utilization of ceramic material provides an efficient,radio-frequency-transparent window for wireless communication with theexternal patient remote and clinician's programmer as the communicationantenna is housed inside the hermetic ceramic case. This ceramic windowhas further facilitated miniaturization of the implant while maintainingan efficient, radio-frequency-transparent window for long term andreliable wireless communication between the IPG and externalcontrollers, such as the patient remote and CP. The IPG's wirelesscommunication is generally stable over the lifetime of the device,unlike prior art products where the communication antenna is placed inthe header outside the hermetic case. The communication reliability ofsuch prior art devices tends to degrade due to the change in dielectricconstant of the header material in the human body over time. The ferritecore is part of the charging coil assembly 95, shown in FIG. 5B, whichis positioned inside the ceramic case 94. The ferrite core concentratesthe magnetic field flux through the ceramic case as opposed to themetallic case portion 97. This configuration maximizes couplingefficiency, which reduces the required magnetic field and in turnreduces device heating during charging. In particular, because themagnetic field flux is oriented in a direction perpendicular to thesmallest metallic cross section area, heating during charging isminimized. It is appreciated that these IPG structures andneurostimulation leads are described for illustrative purposes and thatthe anchoring structures described herein may be used with various otherneurostimulation leads and IPGs in accordance with the principles of theinvention.

The proximal end of the lead include a plurality of conductorscorresponding to the plurality of electrodes at the distal end thatelectrically couple with corresponding contacts within the connectorstack 93 within the header portion 91, thereby electrically connectingthe IPG contacts with the neurostimulation electrodes 30 of the lead 20for delivery of neurostimulation therapy. Although movement in the lowerback region where the IPG is located is limited, the lead may still besubjected to forces and slight movement for various reasons, for exampledue to changes in tissue volume, trauma to the tissue region in whichthe system is implanted, or routine muscle movements. When these forcesand movements are repeated over time, the connection between theproximal portion of the lead and the IPG may become compromised due tothe fatigue caused by repeated stress and strain at the point of thestiffness mismatch that exists at the junction of the flexible lead andthe IPG header portion 91. In some embodiments, a strain relief elementthat extends along a proximal portion of the lead where the lead exitsthe header portion 91 is included to provide strain relief at thejunction of the proximal portion of the lead and the IPG so as tomaintain integrity of the electrical connection and lengthen the usefullife of the lead.

In some embodiments, the system includes a strain relief element thatextends along a proximal portion of the lead adjacent the head portionof the IPG. The strain relief element may be disposed about the proximalportion of the lead or integrated into the lead itself. The strainrelief element may include a proximal base that attaches or interfaceswith a head portion of the IPG. In some embodiments, the strain reliefelement is a helical element that extends about the proximal portion ofthe lead. The strain relief element may be formed of a metal (e.g.stainless steel), polymer or any other suitable material. The proximalportion of the lead may include a recessed portion in which the strainrelief element reside so that the outer surface of the strain reliefelement is substantially flush or about flush with the outer surface ofthe lead. Alternatively, the strain relief element may be applied to anon-recessed or standard sized portion anywhere along the lead body asneeded. Typically, the strain relief element is a length within a rangeof about 1 inch to 6 inches so as to reduce flexing or bending of theproximal portion of the lead near the IPG, which can compromise theelectrical connection over time. In one aspect, the strain reliefelement is formed so as to have an increased stiffness along alongitudinal axis so as to inhibit lateral bending of the proximalportion of the lead. Any of the aspects described herein in regard tothe structure and design of the helical anchor body may be applicable tothe strain relief element.

In some embodiments, the strain relief element 27 comprises a helicalstructure that extends along a proximal portion of the lead 20 adjacentwhere the lead 20 is inserted into the head portion 91 of the IPG 90,such as shown in FIG. 6C. The strain relief element 27 may include aproximal base 28 configured to securely attach to the header portion 91and a helical portion 29 that encircles a proximal portion of the lead.Typically, the helical portion 29 exhibits increased stiffness ascompared to the lead such that the helical portion 29 withstands anystresses or forces applied to the lead in the proximal region.Furthermore the helical structure limits the minimum bending radius inthe region, which prevents sharp bends that can potentially damage thelead at the strain relief location. The strain relief element may beformed of any suitable, biocompatible material, including polymers orvarious metals (e.g. stainless steel, Nitinol). The strain relief membercan be attached to the lead at manufacturing or alternatively, loadedonto the lead at the time of implant and attachment to the IPGconnector.

In one aspect, the strain relief element is sufficiently thin such thatits low profile does not substantially increase the maximumcross-section or crossing profile of the lead through the sheath. Insome embodiments, the proximal portion of the lead may have a reduceddiameter and dimension so as to fittingly receive the strain reliefmember so that the strain relief member is substantially flush with theouter surface of the lead distal of the strain relief member.

FIGS. 6A-6B illustrate detail views of example strain relief members 27and 27′, respectively, each including a proximal base 28 for securing tothe IPG header portion and a helical strain relief portion 29 forwrapping about the proximal portion of the lead 20. The proximal baseportion 28 may be sized and dimensioned according to a particular IPGheader portion. In one aspect, the helical portions 29 can be configuredto provide variable stiffness along the length of the proximal portionof the lead. For example, the helical portions 29 can be of variablethickness along the length of the strain relief to provide gradualstiffness transition in the region and/or the helical portions can varyin pitch and/or width along the length of the strain relief to providegradual stiffness and limit the bend radius in the region. In anotheraspect, the strain relief element 27 can include one or more tines (notshown), similar to the anchors described herein, so as to provide tissuefixation to the strain relief portion and further inhibit movement ormigration of the proximal portion of the lead.

III. Lead Affixation by Helical Anchors

FIG. 7 illustrates a detail view of a neurostimulation lead 20, similarto that in FIG. 4, with an anchoring body 10 mounted on an anchoringportion 22 of the lead, shown in the deployed configuration. As can beseen, the helical body 12 is helically swept about a centrallongitudinal axis for placement on the lead body and the plurality oftines 14 are distributed along the helical body 12 extending laterallyoutward from the central axis and angled in a proximal direction. Asshown in the detail view of 10 FIG. 8, the plurality of tines 14 of theanchoring body are distributed so as to be radially offset from oneanother at regular intervals (e.g. 30°, 45°, 90°) within a range ofintervals, such as between 10° and 90°, so that the plurality of tinesextend outward in different directions circumferentially about thecentral axis. This distributes any anchoring forces about the lead bodyso as to improve anchoring of the lead.

In one aspect, the anchor 10 includes a radiopaque strip 16 embeddedwithin the helical body 12 to allow localization of the anchor 10through visualization techniques. The radiopaque strip may be fabricatedfrom any radiopaque material, such as a platinum alloy (e.g. Pt/lr), soas to visible using standard visualization techniques. Such a strip isadvantageous as it facilitates positioning of the lead at the targetedlocation. In other embodiments, the helical body may be formed of amaterial that is radiopaque, for example a radiopaque material may beblended into a polymer material of which the anchor is formed.

FIGS. 9A-9B illustrate a neurostimulation lead having an attached anchorin a delivery configuration and a deployed configuration, respectively.In FIG. 9A, the plurality of tines 14 are folded against the body of thelead 20 without overlapping each other or an adjacent section of thehelical body. Typically, the tines are constrained in the deliveryconfiguration by an outer sheath (not shown) while the lead is advancedthrough a tunnel in a tissue to the targeted location. The helical bodyis swept at a pitch to allow sufficient space between adjacent turns ofthe helical body for a tab to fold inward against the lead boy, whichallows for a reduced delivery profile. In one aspect, the cross sectionof the anchor is less than 2.0 mm, sufficiently small to be deliveredthrough a 5 French sheath. In one aspect, the lead body includes arecessed portion 22 having a reduced outer diameter, in which thehelical body 12 is attached. This feature facilitates coupling betweenthe anchor 10 and the lead body 20 as the proximal and distal ends ofthe anchor abut against the proximal and distal ends of the recessedportion and allow for a reduced cross-section or crossing profile of theanchor portion of the lead. Once delivery of the electrodes to thetarget location is confirmed, the sheath may be withdrawn proximally,thereby allowing the plurality of tines to resiliently return to thedeployed configuration toward which they are biased, as shown in FIG.9B.

FIGS. 10A-10B illustrate detail views of the anchor 10 shown in FIG. 9Bin the deployed configuration. In this embodiment, the tines 14 are allinclined proximally. It is understood, however, that in otherembodiments, the anchor 10 may be configured so that the tines areangled distally or proximally, extend perpendicular to the longitudinalaxis of the helical body, or extend in multiple differing directions asdesired for a particular application.

In one aspect, the anchor is fabricated from a material sufficientlystiff to exert adequate anchoring forces to maintain the lead in place,yet sufficiently flexibly to fold inward against the lead and to avoiddamaging tissue should the lead be removed from the tissue. In someembodiments, the anchor is fabricated from a molded polyurethane havinga shore hardness within a range between 50 A and 80 D, preferably about70 D. The helical body may have a width between 1.0 mm to 3.0 mm,preferably about 2.0 mm and a total length between 10 mm and 30 mm,preferably about 20 mm. The anchor is configured such that the crossingprofile is less than 2.0 mm, preferably 1.7 mm or less, so that a leadhaving the anchor attached thereto can be delivered through a standardsheath, such as a 5 French sheath. In certain embodiments, the tineshave a length between 1 mm and 3 mm, preferably about 1.8 mm; a widthbetween 0.5 and 2.0 mm, preferably about 0.8 mm; and a thickness between0.2 mm and 0.5 mm, preferably about 0.3 mm. In certain embodiments, theanchor includes between 10 and 20 tines, preferably about 12 to 16tines, spaced apart along the length of the helical body so as to extendin different directions circumferentially about the lead. In someembodiments, the tines are all of the same length and angle in the samedirection, while in other embodiments, the tines may be of varyinglengths, widths and may angle in both proximal and distal directions.While it is advantageous to dimension any of the anchor described hereinaccording to the above described configuration in order to facilitatedelivery of the anchor through a 5 French sheath, it is appreciated thatthe anchor may be configured according to various other dimensions(length, number of tines, etc.) as desired for a particular applicationor neurostimulation lead.

FIGS. 10A-10B and 11A-11B illustrate example anchors, similar to thatshown in FIG. 8, except the tines 14 are formed in differing shapes. Forexample, in one aspect, the tines may be formed such that an end face isangled or pointed, such as shown in FIG. 8. In another aspect, the tinescan be formed in a generally rectangular shape, such as shown in FIGS.10A-10B. In another aspect, the tines can be formed such that thecorners and/or edges are curved, rounded or chamfered, such as shown inFIGS. 11A-11B. This feature may help reduce the possibility of trauma toadjacent tissues by corners or edges of the tines as they engage tissueduring anchoring of the lead.

FIGS. 12A-12B illustrate an example anchor similar to that in FIG. 8except the plurality of tines angle in both proximal and distaldirections. As can be seen, the proximal most tines angle in a distaldirection, while the remaining tines angle in a proximal direction. Thisaspect is useful in applications where the lead tends to experienceforces in both proximal and distal directions. For example, whilestudies have shown that neurostimulation leads implanted through asacral foramen experience primarily forces directed in a proximaldirection, various other applications, such as a peripherally implantedlead in an arm or leg, may experience significant forces in bothproximal and distal directions.

FIGS. 13A-13B illustrate an anchor 10 composed of multiple anchorsections 10′. As shown, the anchor consists of two sections joinedtogether. The anchor sections 10′ may be modular allowing one or moreanchor sections to be used on a lead, as needed for a particular lead orapplication. The anchor sections may include a means to attach or couplethe sections to one another or may be bonded together by various methodsknown to one of skill in the art, such as by use of an adhesive, amechanical or chemical coupling, or an oxidation bonding method. Thisfeature may allow a user to customize an anchoring portion with asdesired, according to differing lengths, as well as differing dimensionsand/or directions of the tines.

FIG. 14A-14B illustrates an anchor 10 having a cork-screw type shape.The anchor includes a continuous helical flap having multiple sectionsdefined by cuts into the helical flap into multiple sections that canfold toward the lead body without overlapping one another. In oneaspect, the anchor 10 is formed from monolithically from a singleintegral component. For example, the anchor 10 may be formed from acork-screw type structure in which the helical flap is separated intotines by wedge-shaped notches 15 cut into the helical flap to definemultiple tines 14 that can fold down against the lead for delivery ofthe anchor through a constraining insertion sheath.

In another aspect, any of the anchors described herein may include oneor more various other features, including: biodegradable tines, drugeluting tines, and flexible dish-like tines that open or collapse aftera certain bend angle is reached to allow for easy insertion orretraction. In another aspect, the anchor may include a strip orembedded material that shield or disrupts MRI induced heating.

In one aspect, the anchor 10 includes one or more drug elutingcomponents, that release one or more therapeutic compounds over a periodof time after implantation. Such a drug eluting component may include aportion of the anchor, a strip intertwined along a length of the anchor,the material from which the anchor is formed, or a coating deposited onthe anchor or portion thereof. For example, the drug or therapeuticcompound can be sprayed onto the anchor, the anchor can be dipped in thedrug or compound, or the drug or compound can be mixed into a polymer ofwhich the anchor is formed. In some embodiments, the anchor may beformed of a bioabsorable or nonabsorable polymer material or acombination of a nonabsorable base coated with a layer of drug elutingpolymer. In one aspect, the drug or therapeutic compound may be appliedin order to promote release of the drug in particular direction, forexample the drug or compound may be applied to promote isotropic oranisotropic release of the drug along the axis of the tines. The elutingdrug may be selected to promote and shorten healing time in order tominimize risk of lead migration. Alternatively or in addition to, theanchor may be configured to elute various other drugs to provide variousother therapeutic benefits. For example, the anchor 10 may be formed toelute a compound to promote fixation within the tissues, such as abiological adhesive or compound to promote tissue formation afterimplantation in order to further minimize risk of lead migration.

While in many of the embodiments shown, the tines are configured toprotrude and fold along an axis parallel to the longitudinal axis alongwhich the helical portion extends, in some embodiments, the anchor canbe designed so that the tines fold inward along a helical or inclinedaxis. Such a configuration can allow the tines to be retracted bytwisting the lead in one direction to facilitate removal of the leadand/or allow the tines to be further deployed by twisting the lead in anopposite direction. In other embodiments, such as those in which thetines fold along an axis parallel to the longitudinal axis, the tinesmay be sufficiently flexible and/or frangible to allow removal of thelead by merely retracting the lead with sufficient force.

In one aspect, the anchor may be formed by cutting a pattern into anintegral piece of material, for example a shape-memory metal, such asNitinol. For example, the anchor can be formed by laser cutting ahelical pattern into a piece of tubing or a cylindrical piece of thematerial, the pattern corresponding to the anchor in the constrainedconfiguration, such as shown in the example of FIG. 15B. The tines canthen be supported on a mold or propped up by various other means so thatthe material can be heat set while the anchor is in the expandedconfiguration, such as shown in FIG. 15A. Typically, the pattern isdefined so that the tines are distributed evenly along the length of thehelical body with the tines extending out in a multi-radial directionalong the sweep of the spiral to provide evenly distributed tissuefixation in all directions, as shown in FIG. 15C.

In one aspect, the helical base can be heat set to a smaller insidediameter than the lead body so as to provide an interference fit, whichcan then be twisted to open and then loaded onto the lead body. Uponrelease, the helical base automatically tightens onto the lead bodyproviding a secure attachment to the lead. The spiral design isconfigured so that when the tines are folded down the tines do notoverlap each other or the helical body of the anchor.

In another aspect, as shown in FIG. 15A, the anchor design can includeone or more retention features 11, 13 at the proximal and distal ends,respectively, that enable precise loading of the anchor onto the device.In this embodiment, the proximal and distal retention features 11,13 aredesigned to abut against a corresponding proximal and distal end of areduced diameter anchoring portion 22 of the lead in which the anchor 10is received so as to affix the anchor 10 to the body of the lead 20 andprevent axial movement of the anchor 10 along the lead before, duringand/or after delivery of the lead and deployment of the anchor 10. Inanother aspect, the proximal and distal retention features 11, 13 may bedesigned in various shapes (e.g. zig-zag, curved, angled) along theproximal and distal facing edges so as to interlock with correspondingshapes along the lead at the proximal and distal ends of the anchoringportion 22. This configuration is useful in preventing free rotationalmovement of the anchor 10 relative the lead body 20 or to assist intranslating rotational movement to the anchor upon rotation of the lead.

In one aspect, the anchor 10 may be formed of any type of implantablebiocompatible polymers. Radiopaque fillers such as barium sulfate,bismuth, and tungsten can be added to the polymer to make the tinesradiopaque under x-ray. Alternatively, or in addition to, a ribbon ofradiopaque metal such as gold or platinum can be imbedded into the bodyof the helix to add radiopacity to the tines. In another approach, theanchor may include one or more discrete radiopaque markers that can beused with visualization techniques for localization of the anchor orthat can be used to determine when the tines are deployed. For example,by placing one of a pair of markers at the end of a tine and the otheron the helical body directly adjacent the end of the tine, when theanchor is in the constrained configuration, separation of the pair ofmarkers can indicate when the tines are deployed, as well as the extentof their deployment within the tissue.

FIG. 16A illustrate another approach by which the anchor 10 can beformed. As shown in FIG. 16A, the anchor may be cut from a length ofextruded polymer tubing, for example by laser cutting. The tines can besubsequently shaped to have an outwardly protruding bias through a heatset or reflow process. For example, the anchor 10 can be mounted on aninternal mold (not shown) that props up the tines in an outwardlyprotruding configuration corresponding to the deployed anchorconfiguration and the polymer is heated and allowed to set. Aftersetting, the tines 14 of the anchor 10 are biased towards the deployedconfiguration, such as shown in FIG. 16B. In one aspect, this heatingand reflow process can also be used to incorporate one or moreradiopaque markers, such as a Pt/Ir wire or ribbon wrapped at the samepitch as the helix. In another aspect, the polymer tubing extrusion canincorporate a ribbon or coil (e.g. nitinol or gold) ribbon to provideself expanding or self closure shape memory element to the anchor tines.Laser cutting can be programming to cut around the embedded ribbon wireto include the wire into the body of the helix.

FIG. 17A-17B illustrate yet another approach by which the anchor 10 maybe formed. Helical anchors, such as any of those described herein, canbe formed by injection molding using a multi-piece mold design. Forexample, two, three or four piece mold designs can be used to mold theanchors as a single integral component. In one aspect, the mold can beconfigured so as to release the anchor at an angle that is specific tothe design of the anchors. A shown in FIG. 17A, a three-piece mold 17 isused to form anchor 10 by an injection molding process. A core pin 18 isused along with the mold to form the open lumen of the anchor. FIG. 17Bshows a four piece mold design 17′ also configured for use with the corepin 18 to allow formation of an anchor 10 through an injection moldingprocess. One advantage to using an injection molding process to form theanchor, is that molded anchors can have variable thickness along thelength of the component. For example, such an anchor can be formed sothat the base is thinner to improve crossing profile and the protrudingtines are thicker to provide retention strength after implantation. Inanother aspect, a metallic element can be incorporated along the entirelength, at the location of the tines, or in the distal and proximal endsfor radiopacity.

Methods of forming anchor in accordance with aspects of the inventiondescribed above are shown in the examples of FIG. 18-19. The examplemethod of FIG. 18 includes method steps of: laser cutting a helicalpattern into a tubular section of material, the pattern corresponding toan neurostimulation lead anchor having a plurality of tines in aconstrained configuration 180; supporting the tines of the tubularsection in an outwardly protruding position corresponding to a deployedconfiguration of the anchor 182; and heat setting the tubular sectionwhile the tines are supported thereby setting the material while theanchor is in the deployed configuration 184. In one aspect, the materialis Nitinol, preferably in the superelastic phase and having anaustentitic finish temperature from about 15 degrees C. to about 35degrees C., so that the anchor will return to the deployed configurationupon heating in the body. In another aspect, the material may be formedof a polymer material that can be set in the deployed configuration byheating and reflow. The methods may be provided to a user to apply tothe lead, or may be affixed to the lead before shipment to the user bywrapping the anchor about an anchoring portion 186. The example methodof FIG. 19 includes steps of: assembling a multi-piece mold defining anouter surface of a helical anchor having a plurality of outwardlyextending tines with a central core pin defining a central lumen of theanchor 190; injecting the flowable material into the assembled mold andallowing the material to at least partly set 194; and removing the moldto release the anchor 196. In some embodiments, the molds are configuredsuch that the outer pieces of the mold are removed along a direction inwhich the tines extend, which reduces the stress and forces applied tothe tines during removal. In some embodiments, a radiopaque ribbonwithin the mold during assembly and/or adding a radiopaque material to aflowable material for forming the anchor 192. Again, the anchor may beprovided to the user for assembly with the lead or applied to the lead198 and supplied to the user assembled with the lead. In another aspect,the anchor may be provided with the lead within a constraining sheathready for insertion into the patient according to the implantationmethods described herein.

Methods of affixing an implanted neurostimulation lead using an anchorin accordance with aspects of the invention are show in the examples ofFIGS. 20-21. The example method of FIG. 20 includes steps of: providinga neurostimulation lead having one or more neurostimulation electrodesand an anchor proximal the one or more electrodes, the anchor includinga helical body wrapped along a length of the lead and one or more oftines attached to the helical body folded inward against the lead bodythe helical body constrained by a sheath 210; advancing the lead througha tissue of a patient to a target location while the one or more tinesare folded inward against the lead body constrained by the sheath 212;resiliently deploying the one or more tines to a deployed configurationextended laterally outward from the helical body by withdrawing thesheath 214; and anchoring the neurostimulation lead at the targetlocation by engaging the one or more tines in the deployed configurationagainst adjacent tissues thereby inhibiting axial movement of the lead216. Lead removal may be effected by proximally withdrawing the leaduntil the anchoring force provided by the flexible tines is overcome.Thus, the tines are fabricated from a material having sufficientstiffness to provide a desired anchoring force but flexible enough toavoid tissue damage when withdrawn.

In the foregoing specification, the invention is described withreference to specific embodiments thereof, but those skilled in the artwill recognize that the invention is not limited thereto. Variousfeatures and aspects of the above-described invention can be usedindividually or jointly. Further, the invention can be utilized in anynumber of environments and applications beyond those described hereinwithout departing from the broader spirit and scope of thespecification. The specification and drawings are, accordingly, to beregarded as illustrative rather than restrictive. It will be recognizedthat the terms “comprising,” “including,” and “having,” as used herein,are specifically intended to be read as open-ended terms of art.

What is claimed is:
 1. A method of anchoring an implantedneurostimulation lead of a neurostimulation system in a patient, themethod comprising: providing a neurostimulation lead having one or moreneurostimulation electrodes and an anchor proximal the one or moreelectrodes, wherein the anchor includes a helical body wrapped along alength of the lead and a plurality of tines attached to the helical bodyfolded inward against a lead body and constrained by a sheath, whereinthe helical body attaches to the lead body in a recessed portion thereofso as to allow for a reduced delivery profile; advancing the leadthrough a tissue of a patient to a target location while the pluralityof tines are folded inward against the lead body constrained by thesheath; resiliently deploying the plurality of tines to a deployedconfiguration extended laterally outward from the helical body bywithdrawing the sheath; and anchoring the neurostimulation lead at thetarget location by engaging the plurality of tines in the deployedconfiguration against adjacent tissues thereby inhibiting axial movementof the implanted lead.
 2. The method of claim 1 wherein the targetlocation comprises a sacral nerve for a neurostimulation treatment ofoveractive bladder (OAB) so that advancing the lead through the tissuecomprises advancing the lead through an S3 foramen until the one or moreneurostimulation electrodes are positioned at the sacral nerve.
 3. Themethod of claim 2, wherein anchoring the neurostimulation lead byengaging the plurality of tines against adjacent tissues comprisesengaging tissues within and/or adjacent the S3 foramen.
 4. The method ofclaim 1, wherein resiliently deploying the plurality of tines compriseswithdrawing the sheath after positioning one or more neurostimulationelectrodes of the lead along a target nerve.
 5. The method of claim 1,wherein resiliently deploying the plurality of tines comprises observingone or more radiopaque markers on the anchor with visualizationtechniques.
 6. The method of claim 1, wherein resiliently deploying theplurality of tines comprises observing a separation of a firstradiopaque markers on at least one tine of the plurality of tines and asecond radiopaque marker on the helical body, wherein the separation isindicative of an extent of deployment.
 7. The method of claim 4, whereinthe one or more neurostimulation electrodes comprises a plurality ofelectrodes, the method further comprising: positioning the lead so thata set of the plurality of electrodes are disposed along the targetednerve.
 8. The method of claim 7, wherein anchoring the neurostimulationlead comprises maintaining the set of the plurality of electrodes alongthe targeted nerve by engagement of the plurality of tines in thedeployed configuration with adjacent tissues.
 9. The method of claim 1,wherein during advancing the lead, the plurality of tines are foldedagainst the lead body without overlapping with one another so as allowfor a reduced delivery profile.
 10. The method of claim 1, wherein therecessed portion is defined so that the anchor is about flush with anouter surface of the lead body outside of the recessed portion.
 11. Themethod of claim 1, wherein the sheath has a diameter of 5 French orhigher.
 12. The method of claim 1, wherein the anchor has a crosssectional profile of about 2 mm or less.
 13. A method of anchoring animplanted neurostimulation lead of a neurostimulation system in apatient, the method comprising: providing a neurostimulation lead havingone or more neurostimulation electrodes and a plurality of tinesextending outwardly from a leady body of the lead; advancing the leadthrough a tissue of a patient to a target location while the pluralityof tines are folded inward toward the lead body constrained by a sheath;resiliently deploying the plurality of tines to a deployed configurationextended laterally outward from the lead body by withdrawing the sheath;coupling neurostimulation lead to a pulse generator; and anchoring theneurostimulation lead at the target location by engaging the pluralityof tines in the deployed configuration against adjacent tissues therebyinhibiting axial movement of the implanted lead and relieving strainwithin a proximal portion of the lead proximal of the one or moreneurostimulation electrodes with a strain relief member comprising ahelical element wrapped along the proximal portion of the lead adjacenta junction of the neurostimulation lead and the pulse generator.
 14. Themethod of claim 13, wherein the strain relief member has variablestiffness along a longitudinal axis thereof so that relieving strain isvariable along the proximal portion of the lead.
 15. A method ofanchoring an implanted neurostimulation lead of a neurostimulationsystem in a patient, the method comprising: providing a neurostimulationlead having one or more neurostimulation electrodes and an anchorproximal the one or more electrodes, wherein the anchor includes ahelical body wrapped along a length of the lead and a plurality of tinesattached to the helical body; advancing the lead through a tissue of apatient to a target location while the plurality of tines are foldedinward toward the lead body; resiliently deploying the plurality oftines to a deployed configuration extended laterally outward from thehelical body by twisting the lead body in one direction, the pluralityof tines being configured to fold inward along a helical or inclinedaxis; and anchoring the neurostimulation lead at the target location byengaging the plurality of tines in the deployed configuration againstadjacent tissues thereby inhibiting axial movement of the implantedlead.
 16. The method of claim 15, wherein during advancing the lead, theplurality of tines are folded against the lead body without overlappingthe anchor so as to allow for a reduced delivery profile.
 17. The methodof claim 15, wherein anchoring the neurostimulation lead furthercomprises relieving strain within a portion of the lead proximal of theone or more neurostimulation electrodes with a strain relief memberdisposed along the proximal portion of the lead adjacent a junction ofthe lead and an external pulse generator.
 18. The method of claim 15further comprising: removing the lead after deployment of the anchor byretracting the plurality of tines from a deployed configuration bytwisting the lead body in an opposite direction as the one direction tofacilitate folding the plurality of tines inward along the helical orinclined axis.
 19. A method of anchoring an implanted neurostimulationlead of a neurostimulation system in a patient, the method comprising:providing a neurostimulation lead having one or more neurostimulationelectrodes and an anchor proximal the one or more electrodes, whereinthe anchor includes a helical body wrapped along a length of the leadand a plurality of tines attached to the helical body; advancing thelead through a tissue of a patient to a target location while theplurality of tines are folded inward toward the lead body; resilientlydeploying the plurality of tines to a deployed configuration extendedlaterally outward from the helical body; and removing the lead afterdeployment of the anchor by retracting the plurality of tines from adeployed configuration by twisting the lead body in one direction, theplurality of tines being configured to fold inward along a helical orinclined axis.